It seems when saving the wp-config.php file the site becomes unavailable due to the file saved not having the slashes stripped correctly

Your plugin is turning this:
define('DB_NAME', 'abc123');

into this:
define(\'DB_NAME\', \'abc123\');

For everything in the file that uses quotes.

Which causes this error, making the site completely inaccessible. The plugin has great potential and very hopeful for what it can become, but this is a huge issue that need to be resolved asap.